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The group delay and phase delay properties of a linear time-invariant (LTI) system are functions of frequency, giving the time from when a frequency component of a time varying physical quantity—for example a voltage signal—appears at the LTI system input, to the time when a copy of that same frequency component—perhaps of a different physical phenomenon—appears at the LTI system output.
Spectral Interferometry has gained momentum in recent years. It is frequently used for measuring the linear response of materials, such as the thickness and refractive index of normal dispersive materials, [8] the amplitude and phase of the electric field in semiconductor nanostructures [9] and the group delay on laser mirrors.
where () is the analytic signal representing the unknown (upconverted) field being measured, is the spectral shear, is the time delay, () = | | is the spectral intensity and () is the spectral phase. For a sufficiently large delay (from 10 to 1000 times the Fourier transform limited [FTL] pulse duration), the interference of the two time ...
Figure 1. The light path through a Michelson interferometer.The two light rays with a common source combine at the half-silvered mirror to reach the detector. They may either interfere constructively (strengthening in intensity) if their light waves arrive in phase, or interfere destructively (weakening in intensity) if they arrive out of phase, depending on the exact distances between the ...
The Mach–Zehnder interferometer is a device used to determine the relative phase shift variations between two collimated beams derived by splitting light from a single source. The interferometer has been used, among other things, to measure phase shifts between the two beams caused by a sample or a change in length of one of the paths.
Roger Jennison developed this novel technique for obtaining information about visibility phases in an interferometer when delay errors are present. Although his initial laboratory measurements of closure phase had been done at optical wavelengths, he foresaw greater potential for his technique in radio interferometry. In 1958 he demonstrated ...
A delay line interferometer (DLI) can be a Mach–Zehnder interferometer or Michelson interferometer based on two-beam interference, in which one beam is time-delayed to the other by a desired interval. Delay line interferometers are also known as optical DPSK demodulators. They convert a phase-keyed signal into an amplitude-keyed signal.
In a typical multi-shot FROG setup, the unknown pulse is split into two copies with a beamsplitter. One copy is delayed by a known amount relative to the other. Both pulses are focused to the same point in a nonlinear medium, and the spectrum of the nonlinear signal is measured with a spectrometer. This process is repeated for many delay points.